Antioxidants for mineral oil lubricants and compositions containing the same



Patented June 20, 1950 ANTIOXIDANTS FOR MINERAL OIL LUBRI- CANTS AND COIWPOSITIONS CONTAINING THE SATME Herschel G. Smith, Wallingford, and Troy L. Cantrell, Lansdowne, Pa., and John G. Peters, Audubon, N. J., assignors to Gulf Oil Corporation, Pittsburgh, Pa", a corporation of Pennsylvania No Drawing. Application November 17, 1948, Serial No. 60,624

Claims. I

This invention relates to antioxidants for mineral oil lubricants and compositions containing the same, and more particularly, it relates to addition agents for mineral oil lubricants which inhibit the oxidative deterioration of said lubricants.

In the lubrication of internal combustion engines of all types, particularly when severe operating conditions are encountered, plain mineral lubricating oils often prove unsatisfactory in service because of the oxidative deterioration of the oil, with the attendant deposition on the engine surfaces of varnish, gum or sludge. Furthermore, many lubricating oil compositions which may be highly satisfactory for the lubrication of other mechanisms have been found wholly unsuitable for use as turbine oils.

The formation of varnishes, gums and sludges on engine surfaces is due at least in part to oxidation effects on mineral lubricating oils. In turbine oils the problem of oxidation is further aggravated, because in normal use turbine oils rapidly become contaminated with water.

It is an object of this invention, therefore, to provide an addition agent for mineral oil lubri cants which will inhibit the oxidative deterioration of such lubricants.

It is a further object of this invention to provide improved mineral oil lubricant compositions which are remarkably stable against oxidation under service conditions.

These and other objects are accomplished'by the present invention wherein an addition agent for mineral oil lubricants is prepared by condensing phenyl salicylate, N-dimethylaniline and formaldehyde in the presence of an activated clay catalyst, and recovering the condensation product. The condensation product so obtained is a light-colored product which, when added to mineral oil lubricants, confers a remarkable stability against deterioration by oxidation. Such condensation products and the mineral oil lubricant compositions containing them are believed to be novel and are considered parts of our invention. Contrary to what may be expected from the nature of the reactants, we do not obtain highlycondensed, insoluble resinous products. On the contrary, when theabove reactants are condensed in accordance with our invention, there are obtained light-colored condensation products which are non-resinous and which are readily soluble in mineral oils.

In performing the condensation, the reactants are mixed and heated-to a maximum temperature of 350 F. We have found that if the temperature of 350 F. is exceeded to any substantial extent, the condensation product formed tends to be 2 resinous and insoluble. The preferred tempera- 313166 for the condensation ranges from to The proportions of the reactants may vary over a relatively wide range. For each mol of phenyl salicylate, there is employed 1 to 4 mols of N-dimethylaniline and 1 to 4 mols of formaldehyde. Ordinarily, it is preferred to use from 5 to 10 per cent by weight of the activated clay catalyst, based on the total weight of the reactants. However, smaller amounts, as low as 1 per cent by weight, and larger amounts, as high as 20 per cent by weight, may also be employed; but larger amounts than about 10 per cent by weight are ordinarily not necessary.

In lieu of formaldehyde, any formaldehydeyielding compound, such as paraformaldehyde, dioxymethylene and trioxymethylene may be employed. In such case, the amount of formaldehyde-yielding compound used is based on the equivalent number of mols of formaldehyde yielded within the range of proportions of formaldehyde set forth hereinabove. Accordingly, as used in the appended claims, the term formaldehyde" is intended to include formaldehyde-yielding compounds as well as formaldehyde itself.

Various'activated clay catalysts may be employed in accordance with our invention. Such materials are well known in the art and comprise a natural clay, such as bentonite, fullers earth, fioridin and smectite, which has been acid treated in order to activate the clay. These materials are described in U. S. Patent 1,898,165, for example.

In preparing our new addition agents, the reactants and catalyst are placed into a reaction vessel which is then closed and the mixture heated with agitation until all of the formaldehyde or formaldehyde-yielding compound has been consumed. At this time, the water which is formed as a result of the condensation is removed, preferably under vacuum, and the dehydrated condensation product is then filtered to remove the activated clay catalyst. In some instances, it is desirable to prepare our new addition agent in a concentrate in a mineral lubricating oil which may then be diluted down with additional oil to the concentration desired in the final lubricating composition. In such instances,

the mineral lubricating oil may be added in a suitable amount, say in a weight equal to the weight of reactants, to the reaction mixture in the reaction vessel, and the condensation product obtained will then be a concentrated solution of the addition agent in the mineral lubricating oil.

The condensation products obtained in accordance with our invention are liquids or crystalline solids. While the exact nature of the chemical composition of the condensation products is unknown, all of the three reactants enter into a final unitary product. The exact manner in which the catalyst influences the reaction is unknown. However, regardless of any theory involved, the use of an activated clay catalyst is an essential feature of our invention, since if the catalyst is omitted, black, insoluble, resinous condensation products are obtained.

The following examples illustrate the preparation of our new addition agent.

Example I.---Into an iron reaction vessel, equipped with means for agitation and a reflux condenser, there were placed 214 pounds (1 pound mol) of phenyl salicylate, 484 pounds (4 pound mols) of N-dimethylaniline, 320 pounds (4 pound -mols of anhydrous formaldehyde) of a 37 per cent by weight aqueous solution of formaldehyde, and 67 pounds (6 per cent by weight of the reactants) of Filtrol (an activated clay) as a catalyst. The mixture was agitated and refluxed at 210 F. for 12 hours, and then all water, both that added with the formaldehyde and formed in the reaction, was distilled off by heating at 290 F. and the product dried. The product was then filtered through Celite, a diatomaceous earth filter aid. The product had the following properties:

Gravity, API 0.8 Color, NPA 4.75 Neutralization No. 10.8

Example II.--An addition agent was prepared by reacting 1 mol of phenyl salicylate, 3 mols of formaldehyde and 3 mols of N -dimethylani1ine in the presence of per cent by weight of the total reactants of an activated clay catalyst (Filtrol) under the conditions set forth in Example I. The product had the following properties:

Gravity, API 1.1 Color, NPA 5.0 Neutralization No. 11.2

Example III.An addition agent was prepared by reacting 1 mol of phenyl salicylate, 2 mols of N-dimethylaniline and 4 mols of formaldehyde in the presence of 15 per cent by weight of the total reactants of an activated clay catalyst (Filtrol) under the conditions set forth in Example I. The product had the following properties:

Gravity, API 0.1 Color, NPA 4.5 Neutralization No. 10.7

The condensation products obtained in accordance with the above disclosure from phenyl salicylate, N-dimethylaniline and formaldehyde in the presence of an activated clay catalyst are excellent addition agents for mineral oil lubricants. They are readily soluble in all types of mineral oils, that is, paraflinic, naphthenic or mixed base mineral oils and can be blended with mineral oils in high proportions to form concentrated solutions thereof, which may then be diluted down to the proportions desired in the final mineral oil lubricant composition. As stated, our new addition agents are remarkably effective in inhibiting the oxidative deterioration of mineral oil lubricant compositions. For this purpose small amounts of our new addition agents are generally suflicient. For example, our addition agents may be added to mineral lubricating oils in minor amounts, say from 0.001 to l per cent by weight of our new addition agents may be used if desired but it is ordinarily unnecessary to do so.

The following examples illustrate the remarkable antioxidant effects of our new addition agents. In the following examples, the base oil and the same oil blended with our new addition agents are subjected to a standard oxidation test which measures the stability of the oils to oxidation. The oxidation test referred to is a standard test designated ABTM D943-47'1. Briefly, the test comprises subjecting the oil sample to oxygen at a temperature of C. (203 F.) in the presence of water and an iron-copper catalyst, and determining the time required to build up a neutralization number of 2. The flow of oxygen is maintained at 3 liters per hour. The remarkably effective stability to oxidation of mineral oil lubricant compositions containing our new addition agents is illustrated by the results shown in the following examples.

Example IV.To a refined motor oil base, there was added 0.5 per cent by weight of the addition agent prepared in accordance with Example I. A comparison of the base oil and improved oil follows:

Example V.An improved steam turbine oil was prepared by adding 0.5 per cent by weight of the addition agent prepared in accordance with Example I to a turbine 011 base. A comparison of the base oil and the base oil blended with the antioxidant showed the following results:

Base Improved Oil Oil Gravity, API 27. 5 27. 3 Oxidation Test, ABTM D943-47'I:

203 F., 3 L. Oxygen per Hr.-

Time Oxidimd. Hrs 180 3, 275 Neutralization N0 2.0 2.0

The above examples show the remarkable oxidation stability imparted to mineral oil lubricant compositions by the use of our new addition agents. Mineral oil lubricant compositions containing our new addition agents are therefore eminently suited for use where the operating conditions are extremely severe, as in Diesel, tank and truck engines, and in the lubrication of steam turbines.

The notable antioxidant effects of our new addition agents cannot be readily accounted for and cannot be predicted from the nature of the reactants. Thus, condensation products prepared from other functionally similar compounds have been found to be either pro-oxidant or to show no antioxidant effects whatsoever. For example, we have prepared a condensation product similar to our new addition agent by substituting xylidine for N-dimethylaniline. The resulting condensation product was found to be entirely unsuitable for inhibiting the oxidative deterioration of mineral oil lubricant compositions.

While we have shown in the examples the preparation of compounded lubricating oils, our invention is not limited thereto but comprises all mineral oil lubricant compositions containing our new addition agents, such as greases and the like. If desired, other known addition agents may be incorporated into the lubricant compositions prepared in accordance with our invention. For example, pour point depressants, extreme-pressure agents, viscosity index improvers and the like may be added.

Resort may be had to such modifications and variations as fall within the spirit of the invention and the scope of the appended claims.

We claim:

1. The process of preparing an addition agent for mineral oil lubricants which comprises heating phenyl salicylate with from 1 to 4 mols of N-dimethylaniline and 1 to 4 mols of formaldehyde per mol of phenyl salicylate in the presence of an activated clay catalyst at a temperature not in excess of 350 F. to condense together the three reactants. and recovering the condensation product.

2. The process of preparing an addition agent for mineral oil lubricants which comprises heating phenyl salicylate with from 1 to 4 mols of N-dimethylaniline and 1 to 4 mols of formaldehyde per mol of phenyl salicylate in the presence of 5 to 10 per cent by weight on the total reactants of an activated clay catalyst at a temperature of from 150 to 300 F. to condense together the three reactants, and recovering the condensation product.

3. The process of preparing an addition agent for mineral oil lubricants which comprises adding an activated clay catalyst, phenyl salicylate with from 1 to 4 mols of N-dimethylaniline and l to 4 mols of formaldehyde per mol of phenyl salicylate to a mineral lubricating oil, heating the mixture to a temperature not in excess of 350 F. to form a condensation product of the three reactants, and recovering a solution of the condensation product in the mineral lubricating oil.

4. The process of preparing an addition agent for mineral oil lubricantswhich comprises heating 1 mol of phenyl salicylate, 4 mols of N-dimethylaniline, and 4 mols of formaldehyde in the presence of about 6 per cent by weight on the total reactants of an activated clay catalyst at a temperature of from 150 to 300 F. to condense together the three reactants, and recovering the condensation product.

5. The process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol of phenyl salicylate, 3 mols of N-dimethylaniline, and 3 mols of formaldehyde in the presence of about 10 per cent by weight on the total reactants of an activated clay catalyst at a temperature of from 150 to 300 F. to condense together the three reactants, and recovering the condensation product.

6. The process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol of phenyl salicylate, 2 mols of N-dimethylaniline, and 4 mols of formaldehyde in the presence of about 15 per cent by weight on the total reactants of an activated clay catalyst at a temperature'of from 150 to 300 F. to condense together the three reactants, and recovering the condensation product.

'7. A non-resinous condensation product of phenyl salicylate with from 1 to 4 mols of N-dimethylaniline and 1 to 4 mols of formaldehyde 3 per mol of phenyl salicylate, said product being obtainable by the process of claim 4'.

8. A non-resinous condensation product of 1 mol of phenyl salicylate, 4 mols of N-.-dimethylaniline and 4 mols of formaldehyde, said product being obtainable by the process of claim 4.

9. A non-resinous condensation product of 1 mol of phenyl salicylate, 3 mols of N-dimethylaniline and 3 mols of formaldehyde, said product being obtainable by the process of claim 5.

10. A non-resinous condensation product of 1 mol of phenyl salicylate, 2 mols of N-dimethylaniline and 4 mols-of formaldehyde, said product being obtainable by the process of claim 6.

11. A lubricant composition comprising a maior amount oi a mineral lubricating oil, and a minor amount, sumcient to inhibit the oxidative deterioration of said oil of a non-resinous condensation product of phenyl salicylate with from 1 to 4 mols of N-dimethylaniline and 1 to 4 mols of formaldehyde per mol of phenyl salicylate, said product being obtainable by the process of claim 1'.

12. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, from 0.001 to 1.0 per cent by weight of said oil, of a non-resinous condensation product of phenyl salicylate with from 1 to 4 mols of N-dimethylaniline and 1 to 4 mols of formaldehyde per mol of phenyl salicylate, said product being obtainable by the process of claim 1.

13. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, sufficient to inhibit the oxidative deterioration of said oil of a non-resinous condensation product of 1 mol of phenyl salicylate, 4 mols of N-dimethylaniline and 4 mols of formaldehyde, said product being obtainable by the process of claim 4.

14. The composition of claim 13, wherein the amount of said non-resinous condensation product is 0.5 per cent by weight of said 011.

15. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, sufilcient to inhibit the oxidative deterioration of said oil, of a non-resinous condensation product of 1 mol of phenyl salicylate, 3 mols of N-dimethylaniline and 8, mols of formaldehyde, said product being'obtainable by the process of claim 5.

16. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, suflicient to inhibit the omdative deterioration of said oil, of a non-resinous condensation product of 1 mol of phenyl salicylate, 2 mols oi. N-dimethylaniline and 4 mols oi. formaldehyde, said product being obtainable by the process of claim 6.

HERSCHEL G. SMITH. TROY L. CANI'REIL. JOHN G. PEI'ERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,594,983 Sommerville Aug. 3, 1928 2,113,599 Musselman Apr. 12, 1938 2.2941726 Dreshfleld "Sept. 1, 1942 2,375,168 Hardman May 1, 1945 2,453,850 Mikeska Nov. 16, 1948 2,454,890 Smith et al. Nov. 30, 1948 Certificate of Correction Patent No. 2,512,445 June 20, 1950 HERSCHEL G. SMITH ET AL. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 2, for the claim reference numeral 4 read 1 and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day of September, A. D, 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent No. 2,512,445 June 20, 1950 HERSCHEL G. SMITH ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 2, for the claim reference numeral 4 read 1 and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 19th day of September, A. D, 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

1. THE PROCESS OF PREPARING AN ADDITION AGENT FOR MINERAL OIL LIBRICANTS WHICH COMPRISES HEATING PHENYL SALICYLATE WITH FROM 1 TO 4 MOLS OF N-DIMETHYLANILINE AND 1 TO 4 MOLS OF FORMALDEHYDE PER MOL OF PHENYL SALICYLATE IN THE PRESENCE OF AN ACTIVATED CLAY CATALYST AT A TEMPERATURE NOT IN EXCESS OF 350*F. TO CONDENSE TOGETHER THE THREE REACTANTS, AND RECOVERING THE CONDENSATION PRODUCT. 